1. Field of the Invention
The invention provides oxide particles with a core of a metal oxide or metalloid oxide, a doping component distributed in the core and a shell surrounding the core.
2. Description of the Background
The persistent trend towards miniaturization in the semiconductor industry leads to ever higher requirements in the chemical-mechanical polishing of oxide and metal layers. The aim of polishing is a rapid, precise removal of the surface without generating scratches, with the highest possible selectivity of the polishing agent towards the various layers required for building up an integrated circuit.
Attempts are made to meet these higher demands on the polishing agent in part by employing physical mixtures of polishing particles for a polishing task, in order thus to combine the particular advantages of the mixture partners. It is often a disadvantage here that parameters which are important for the polishing operation, such as e.g. the particle sizes or the behaviour of the polishing particles at various pH ranges, do not match one another. This means that no stable dispersions for chemical-mechanical polishing can be obtained.
Although uniform particles are present in chemical mixtures of polishing particles, the combination possibilities are limited by the known preparation processes and the availability of the starting materials and the associated profitability of the processes.
A process for the preparation of mixed oxides is described, for example, in EP-A-1048617. In a pyrogenic process, an SiCl4/AlCl3 mixture is brought together in an oxygen/hydrogen flame and a mixed oxide of silicon dioxide and aluminum oxide is obtained in a hydrolysis step. Uniform is to be understood as meaning that a mixed oxide particle consists of the two molecular species SiO2 and Al2O3.
The doped, pyrogenic oxides described in DE-A-196 50 500 extend the range of abrasive particles for chemical-mechanical polishing. The doping component, which is distributed in the entire particle, changes the structure and the properties of the particular particle and therefore the polishing properties, such as rate of removal of material and selectivity. However, the polishing selectivity is not sufficient for uses in chemical-mechanical polishing of very thin layers.